This invention relates to a filler for having a pattern such as grain pattern formed on ceramics product such as toilet stools, washing basins, counters, tiles, accessories, tombstones or craftworks, and relates to a process for producing the same.
In the prior art, as the filler for exhibiting a pattern such as grain pattern on ceramics product, natural raw stone grain, metallic powder and colored fragments of fired ceramic have been used. By kneading these fillers with kneading mud and extruding the mixture, or by mixing them with base material powder and molding the mixture by way of pressing, ceramics products of grain pattern have been obtained.
When natural raw stone grain, metallic powder or colored fragments of fired ceramic, etc. have been used, there has been the problem that warping and cutting are liable to be generated due to the difference in firing shrinkage or expansion coefficient during the firing step. Also, in the case of molding by slip casting, when the particle size of the filler becomes a certain particle size or larger, separation or sedimentation occurs in the slip due to the difference in specific gravity between the filler and the slip for formation of ceramics, whereby it becomes difficult to form a pattern such as uniform grain pattern. Even if it can be formed, the filler comprising raw stone grain, metallic powder and colored fragments of fired ceramic cannot be cut easily, and working and finishing under the state of green base material cannot be easily accomplished. This also posed a similar problem in dried base material, and due to the difference in hardness between the filler such as raw stone grain, metallic powder and colored fragments of fired ceramic and the slip for ceramics molding, cutting, working or finishing of the cast molded product could not be easily accomplished.
Further, in the slip casting step, the conventional filler such as the raw stone grain, metallic powder and colored fragments of fired ceramic and the slip for ceramics molding were poorly compatible with each other due to different material characteristics of the components, whereby there was the problem that cutting or cracking is liable to be generated in the molded product. Further, during the firing step, since the conventional filler and the slip for ceramics molding are different in firing shrinkage and expansion coefficient, warping or cutting, are liable to be generated, whereby there has been the problem that variation of color formation after firing has been limited.